Table_4_Regulation of the Cell Cycle, Apoptosis, and Proline Accumulation Plays an Important Role in the Stress Response of the Eastern Oyster Crassostrea Virginica.xlsx

BackgroundUnderstanding how organisms respond and adapt to environmental changes is central to evolutionary biology. As a sessile organism that has adapted to life in estuaries and intertidal zones, the eastern oyster Crassostrea virginica can tolerate wide fluctuations in temperature and salinity and survive for weeks out of water. To understand the molecular mechanisms underlying the remarkable stress tolerance of the eastern oyster, we studied the transcriptomic changes induced by exposure to air and cold stress. Eastern oysters were maintained for 7 days under four conditions, namely, in seawater (normal) at 22°C, in air at 22°C, in seawater at 5°C and in air at 5°C, and then sampled for RNA sequencing.
ResultsTranscriptomic analysis revealed that many genes involved in cell cycle progression and DNA replication were downregulated in oysters exposed to air and cold, which indicates that stress inhibits cell division. Exposure to air at 22°C induced a concerted inhibition of apoptosis through the upregulation of expanded inhibitors of apoptosis and the downregulation of caspases. Interactions between TNF and NF-κB signalling implied a reduction in the inflammatory response and immune functions. Key genes for proline production, fatty acid synthesis and chromosomal proteins were upregulated during exposure to low temperatures, which suggested that proline accumulation, energy conservation, and epigenetic modification of chromosomes are important for coping with cold stress. The upregulation of melatonin, FMRFamide, and neural acetylcholine receptors indicate the significance of the neurohormonal regulation of homeostasis.
ConclusionThese results show that air exposure and cold stress alter the expression of key genes for cell division, apoptosis, proline accumulation, fatty acid metabolism, neurohormonal signalling, and epigenetic modifications, suggesting regulation of these processes plays an important role in the stress response of the eastern oyster and possibly other marine molluscs. This study provides new insights into molecular mechanisms of stress response that are essential for understanding the adaptive potential of marine organisms under climate change.

研究背景：阐明生物体对环境变化的响应与适应机制，是进化生物学的核心议题。美洲牡蛎（Crassostrea virginica）作为适应河口与潮间带生境的固着生物，可耐受温度与盐度的大幅波动，且能在脱离海水的状态下存活数周。为解析美洲牡蛎卓越抗逆性背后的分子机制，本研究针对空气暴露与低温胁迫诱导的转录组变化展开分析。实验将美洲牡蛎置于四种条件下培养7天：22℃海水（正常对照组）、22℃空气、5℃海水以及5℃空气，随后取样进行RNA测序。
研究结果：转录组分析显示，经空气暴露与低温胁迫处理的牡蛎体内，诸多参与细胞周期进程与DNA复制的基因表达量下调，表明胁迫可抑制细胞分裂。22℃空气暴露可通过上调凋亡抑制因子的表达、下调半胱天冬酶（caspases）的转录水平，协同抑制细胞凋亡。肿瘤坏死因子（TNF）与核因子κB（NF-κB）信号通路的互作分析显示，机体的炎症应答与免疫功能出现下调。低温胁迫处理下，脯氨酸合成、脂肪酸合成以及染色体相关蛋白的关键基因表达量上调，提示脯氨酸积累、能量保存与染色体表观遗传修饰在应对低温胁迫过程中发挥重要作用。褪黑素（melatonin）、FMRF酰胺肽（FMRFamide）以及神经乙酰胆碱受体的表达上调，表明神经激素调控在维持内环境稳态中具有关键意义。
研究结论：本研究结果表明，空气暴露与低温胁迫可调控细胞分裂、细胞凋亡、脯氨酸积累、脂肪酸代谢、神经激素信号通路以及表观遗传修饰相关关键基因的表达，提示上述过程的调控在美洲牡蛎乃至其他海洋软体动物的胁迫应答中发挥重要作用。本研究为胁迫应答的分子机制提供了新视角，这对于理解气候变化下海洋生物的适应潜力具有重要意义。